Boeing's 787 Dreamliner jet has had a lot of troubles lately -- namely with its batteries -- and the last person the aerospace company likely wanted advice from was competitor Elon Musk.

Musk, the CEO of automaker Tesla and private space transport company SpaceX, recently told Flightglobal that the 787 Dreamliner's batteries are "inherently unsafe." His company SpaceX competes with the Boeing/Lockheed Martin partnership, United Launch Alliance, in the aerospace sector.

"Unfortunately, the pack architecture supplied to Boeing is inherently unsafe," said Musk.
"Large cells without enough space between them to isolate against the cell-to-cell thermal domino effect means it is simply a matter of time before there are more incidents of this nature. Moreover, when thermal runaway occurs with a big cell, a proportionately larger amount of energy is released and it is very difficult to prevent that energy from then heating up the neighboring cells and causing a domino effect that results in the entire pack catching fire."

However, Mike Sinnett, Boeing's 787 chief project engineer, defended the design and development of the batteries.

"I design a cell to not fail and then assume it will and then ask the next 'what-if' questions," said Sinnett. "And then I design the batteries that if there is a failure of one cell it won't propagate to another. And then I assume that I am wrong and that it will propagate to another and then I design the enclosure and the redundancy of the equipment to assume that all the cells are involved and the airplane needs to be able to play through that."

Musk's Tesla uses batteries fueled by lithium cobalt oxide, which is what Boeing uses for the 787. Musk understands that these batteries have highly flammable tendencies, and even offered his help to Boeing in its construction, but Boeing declined.

"They [Boeing] believe they have this under control, although I think there is a fundamental safety issue with the architecture of a pack with large cells," said Musk. "It is much harder to maintain an even temperature in a large cell, as the distance from the center of the cell to the edge is much greater, which increases the risk of thermal runaway."

In a recent report by The New York Times, it was discovered that Boeing knew about the battery fire issues in the 787 before this month's problems occurred, which grounded the jets in the U.S., Japan and India.

The report said that Japanese airline All Nippon Airways (ANA) replaced 10 787 batteries from May to December of 2012. Reasons included an unexpectedly low charge in the main battery, batteries that failed to start normally and one battery showing an error reading.

Japan Airline (JAL) also had "several cases" where it had to replace the 787's batteries before the issues that occurred this month, but it didn't disclose an exact number.

The airlines said they reported the incidents' to Boeing, but Boeing felt they didn't need to alert safety regulators because it was not considered a safety issue, but rather "within the scope of regular maintenance" carried out by airline crews.

Since large lithium batteries are a headache -- if not inherently dangerous -- we have to look at alternatives. One is to go back to the heavier nickel-cadmium batteries.Another is to use fuel cells. Fuel cells are now used in warehouse lifts and they supply unattended backup power to cell towers.Why not use them in commercial airplanes? They have proved reliable for over a decade in our space Shuttle.http://spaceflight.nasa.gov/shuttle/reference/shut...What about cost? With $16,000 for a lithium battery, cost is relative. Moreover, fuel cells are now a sixth of what they were five years ago.What about the Hindenburg?Those flames etched in our minds came from the fresh paint on the tarp. Hydrogen itself burns colorless, last about a second, and the flames goes straight up.But where would we store the hydrogen? In tanks of the type now used in fuel cell cars -- and they can be refilled every time the plane refuels.Or we could go with low pressure, though heavier, metal hydride tanks. This could eventually lead to our use of hydrides as artificial muscles -- to operate the plane's wings, brakes and landing gear. Metal hydrides can do this easily by us merely changing the current of the heating element inside the tank.http://news.discovery.com/tech/biotechnology/artif...

The battery in question is actually used just like your car battery to start one of the planes auxiliary motors. That needs a lot power in an instant. I'm not sure fuel cells would be right for this application.

I was a helicopter mechanic for 6 years and our system used a much safer hydraulic starter. Sometimes low tech is the answer, or why not just plug in a ground cart start the engines. This is all pretty standard stuff and a whole lot cheaper.

Great in most cases, but then the plane is limited to airports with that infrastructure.

Also, then you are f'd when the engines shut down in flight and you want to restart them. There have been several cases where hundreds of lives were saved because the engines could be restarted in flight after a failure.

Ram air, you use the forward motion of the plane to get the engines spooling up to starting speeds. If the plane hasn't fallen out of the sky its engines are no doubt already spinning up to speed. If I remember right you only have to spool them up to about 30% of their operating speed to get them started.

The minimum speed required for a windmill start maybe (and probably is) quite a bit higher than the best glide speed.

...and parameter for one engine operation may leave a narrow margin for windmill start of the other engine.

Regardless...the batteries are not used to start the main engines. They are used to start the APU and provide emergency power to things needed at all times like flight controls and high tech computerized glass cockpit in 787 (that would probably take 10 minutes to reboot is power were disrupted). Once the APU is running, an 1100 HP Sunstrand unit in the 787, then that can start the starter/generators on the main turbines.

Of course it was the batteries for the APU that had problems in one the JAL flights....

IIRC the dreamliner carries a 500MW powerplant, if a completely safe helicopter hydraulic starter could have spooled that thing up to speed I'm sure boeing would have chucked it in their design. It's probably not possible though, or at least not within weight limits.

Except the fuel cell design in the Space Shuttle does double-duty. Very simple chemistry formula:

2 H2 + O2 -> energy + 2 H2O

In the Space Shuttle, the fuel cells create both the electric power needed to run its onboard systems, and drinkable water for its crew. Thus the fuel cells make sense.

Now, put that into a 787. Sure, you'll have the power you need, but what are you going to do with the water byproduct? Let's not forget the safety precautions needed to ensure that the hydrogen tank doesn't leak. Those lithium batteries fail and catch fire are bad? If an H2 tank leaks, the whole thing explodes - it's worse than using C4 as the 787's primary insulation material.

You may want to know, there's a lot of hydrogen in jet fuel, being a hydrocarbon and all... :P

A catalyst/reaction chamber can break down the fuel to release hydrogen for use in the fuel cell, or at least crack the hydrocarbon chain to a shorter form that can be used in a fuel cell. Some cells are designed to run on methane I believe.

Why even nimh? Lithium phosphate is almost just as safe as nimh with almost the same power/weight density as lithium ion/cobalt. Even with these potentially explosive batteries that many modern laptop still use, a properly designed charging circuit for these would include individual cell voltage/temp monitoring, should be catching these overheating/overcharging cells, and cutting off the charge before the heat up and explode. Somehow, these batteries are either outright defective or are being overcharged.